var Reindeer = Container.expand(function () {
	var self = Container.call(this);
	if (self.y < self.targetY) {
		self.y += Math.min(self.speed, self.targetY - self.y);
	} else if (self.y > self.targetY) {
		self.y -= Math.min(self.speed, self.y - self.targetY);
	}
	var reindeerGraphics = self.createAsset('reindeer', 'Reindeer on a rocket', .5, .5);
	self.targetY = self.y;
	self.speed = 5;
	self.move = function () {};
});
var Obstacle = Container.expand(function () {
	var self = Container.call(this);
	var obstacleGraphics = self.createAsset('obstacle', 'Obstacle', .5, .5);
	self.speed = -5;
	self.move = function () {
		self.x += self.speed;
	};
});
var Game = Container.expand(function () {
	var self = Container.call(this);
	LK.stageContainer.setBackgroundColor(0x008080);
	var scoreTxt = new Text2('0', {
		size: 150,
		fill: "#ffffff"
	});
	scoreTxt.anchor.set(.5, 0);
	LK.gui.topCenter.addChild(scoreTxt);
	var reindeer = self.addChild(new Reindeer());
	reindeer.x = 2048 / 2;
	reindeer.y = 2732 - 200;
	var obstacles = [];
	var isGameOver = false;
	var tickOffset = 0;
	var score = 0;
	LK.on('tick', function () {
		reindeer.move();
		if (isGameOver) {
			LK.effects.flashScreen(0xff0000, 1000);
			LK.showGameOver();
		} else {
			if (LK.ticks % 60 === 0) {
				score++;
			}
		}
		for (var a = obstacles.length - 1; a >= 0; a--) {
			if (!obstacles[a]) continue;
			obstacles[a].move();
			if (obstacles[a].x < -50) {
				obstacles[a].destroy();
				obstacles.splice(a, 1);
			}
		}
		if (tickOffset++ % 30 == 0) {
			var newObstacle = new Obstacle();
			newObstacle.x = 2048;
			newObstacle.y = Math.random() * 2732;
			obstacles.push(newObstacle);
			self.addChild(newObstacle);
		}
		scoreTxt.setText(score.toString());
		for (var i = 0; i < obstacles.length; i++) {
			if (reindeer.intersects(obstacles[i])) {
				isGameOver = true;
				break;
			}
		}
	});
	stage.on('down', function (obj) {
		var event = obj.event;
		var pos = event.getLocalPosition(self);
		reindeer.targetY = pos.y;
	});
});

===================================================================
--- original.js
+++ change.js
@@ -1,11 +1,15 @@
 var Reindeer = Container.expand(function () {
 	var self = Container.call(this);
+	if (self.y < self.targetY) {
+		self.y += Math.min(self.speed, self.targetY - self.y);
+	} else if (self.y > self.targetY) {
+		self.y -= Math.min(self.speed, self.y - self.targetY);
+	}
 	var reindeerGraphics = self.createAsset('reindeer', 'Reindeer on a rocket', .5, .5);
+	self.targetY = self.y;
 	self.speed = 5;
-	self.move = function () {
-		self.y -= self.speed;
-	};
+	self.move = function () {};
 });
 var Obstacle = Container.expand(function () {
 	var self = Container.call(this);
 	var obstacleGraphics = self.createAsset('obstacle', 'Obstacle', .5, .5);
@@ -65,7 +69,7 @@
 	});
 	stage.on('down', function (obj) {
 		var event = obj.event;
 		var pos = event.getLocalPosition(self);
-		reindeer.y = pos.y;
+		reindeer.targetY = pos.y;
 	});
 });